A tremor is an involuntary, rhythmic muscle contraction resulting in a shaking movement in one or more parts of the body. These movements most commonly affect the hands, but they can also occur in the arms, head, voice, or torso. While minor shaking can be part of the natural aging process, a noticeable tremor is a frequent concern for older adults. Accurate diagnosis is necessary because the tremor’s characteristics often point directly to its origin, guiding appropriate management and treatment.
Essential Tremor
Essential Tremor (ET) is the most common movement disorder, affecting millions worldwide. ET is primarily an “action tremor,” meaning shaking occurs when the affected body part is actively being used or held in a specific posture against gravity. For instance, the tremor is visible when a person is reaching for an object, writing, or holding their arms outstretched. This contrasts with tremors that appear when muscles are completely relaxed.
The frequency of ET is typically higher than other tremors, often ranging from 6 to 12 Hertz (cycles per second). It characteristically affects both sides of the body, though it may begin asymmetrically, and is commonly seen in the hands and forearms. The tremor can also involve the head, often presenting as a “yes-yes” or “no-no” motion, or affect the vocal cords, causing a shaky voice.
Essential tremor is usually a progressive condition, worsening slowly over time and making activities of daily living increasingly difficult. Diagnosis is made clinically by observing the tremor type and ruling out other causes, such as Parkinson’s disease or medication side effects. Formal criteria require a bilateral action tremor for at least three years, with no other apparent neurological symptoms. A strong family history is common, suggesting a significant genetic component, as 50–70% of individuals report an affected relative.
Tremors Associated with Parkinson’s Disease
The tremor associated with Parkinson’s Disease (PD) has distinct characteristics that differentiate it from Essential Tremor. The typical PD tremor is classified as a “rest tremor,” meaning it occurs when the limb is fully supported and at rest. This shaking often diminishes or disappears entirely during intentional movement, such as reaching for a glass. The frequency of this tremor is generally slower, typically ranging from 4 to 6 Hertz.
The tremor usually begins on one side of the body, often in one hand, and may remain asymmetrical or spread to the other side as the disease progresses. A highly recognizable presentation is the “pill-rolling” motion, involving the rhythmic movement of the thumb and forefinger rubbing together. The tremor is only one component of the larger neurological syndrome that defines Parkinson’s Disease.
The presence of other cardinal symptoms is crucial for distinguishing PD from an isolated tremor disorder. These associated features include bradykinesia, which is a slowness of movement affecting fine motor tasks and walking. Patients also experience muscle rigidity (stiffness in the limbs and trunk) and postural instability, leading to difficulty with balance and an increased risk of falls. The combination of a rest tremor with these other neurological signs helps confirm a diagnosis of Parkinson’s Disease.
Non-Neurological and Secondary Triggers
Many tremors are not caused by primary neurological conditions like Essential Tremor or Parkinson’s Disease, but are secondary to other factors. These causes are important to identify because they are often treatable or reversible upon diagnosis and management of the underlying trigger. A common category is medication-induced tremor, which can result from drug classes frequently prescribed to older adults.
Medications that affect the nervous system can induce or worsen a tremor. These include certain mood stabilizers (such as lithium and valproate), some anti-seizure drugs, and various antidepressants (including SSRIs and tricyclic antidepressants). Some antipsychotic medications are also known to cause this side effect. Even common asthma medications, specifically bronchodilators containing beta-agonists, can trigger or enhance a physiological tremor.
Metabolic and systemic imbalances can cause an enhanced physiological tremor, typically presenting as a fine, rapid shaking of the hands. Hyperthyroidism (an overactive thyroid gland) increases the body’s metabolism and sympathetic nervous system activity, which can manifest as a tremor. Similarly, hypoglycemia, or low blood sugar, can induce shaking because muscles are deprived of their necessary energy source.
Beyond medical causes, common lifestyle and environmental factors can temporarily exacerbate an existing tremor. High levels of anxiety, acute emotional stress, and physical fatigue are known to increase the amplitude of physiological shaking. Excessive consumption of caffeine, a potent stimulant, can also heighten the body’s natural tremor. Addressing these modifiable factors can lead to a noticeable reduction in tremor severity.